Freshwater mussels were surveyed in the mainstream Duck River downstream of Centerville, Tennessee, during June and October 2000. A total of 32 species (1 Margaritiferidae and 31 Unionidae) representing 23 genera was found. Comparisons with species reported in the literature revealed that three species, spectaclecase, Margaritinopsis monodonta (Say, 1829); Wabash pigtoe, Fusconaia flava (Rafinesque, 1820); and clubshell, Pleurobema clava (Lamarck, 1819), were new records for the Duck River drainage. One of these, Pleurobema clava, is a federally listed endangered species. Our survey also documented downstream range extensions within the Duck River for six species, Tennessee pigtoe, Fusconaia barnesiana (Lea, 1838); wavyrayed lampmussel, Lampsilis fasciola Rafinesque, 1820; slabside pearlymussel, Lexingtonia dolabelloides (Lea, 1840); Ohio pigtoe, Pleurobema cordatum (Rafinesque, 1820); rabbitsfoot, Quadrula cylindrica (Say, 1817); and painted creekshell, Villosa taeniata (Conrad, 1834). The range extensions included one federally endangered candidate species, Lexingtonia dolabelloides, and the remaining five species are reported by the Tennessee Valley Authority, Natural Heritage Project, as listed or candidates for conservation status by one or more states within their range. The results from this limited survey indicate the presence of unusual mussel diversity and calls attention to the need for increased conservation activities on the Duck River.